ABB Relion 670 series - Page 270

RFPG
X1+Xn
X1+Xn
RFPGR1+RnRFPG
RFPG
RFPG
RFPG
R
X
R1+Rn
(Ohm/loop)
ANSI05000661-3-en.vsd
R0-R1
Rn
3
=
X0-X1
Xn
3
=
j
n
j
n
(Ohm/loop)
ANSI05000661 V3 EN
Figure 132: Characteristic for the phase-to-ground measuring loops, ohm/loop
domain.
The fault loop reach may also be presented as in figure 133.
VA
R1 + j X1
IA
RFPG
Phase-to-ground
fault in phase A
(Arc + tower
resistance)
0
(R0-R1)/3 +
j (X0-X1)/3 )
IN
Phase-to-ground
element
en06000412_ansi.vsd
ANSI06000412 V1 EN
Figure 133: Fault loop model
Section 6 1MRK505222-UUS C
Impedance protection
264
Technical reference manual